Circuit and method for analyzing a patient's heart function using overlapping analysis windows

Abstract

A circuit includes a sensor coupled to a processor. The sensor senses an electrical signal that is representative of a patient parameter, and the processor determines a condition of the patient by analyzing first and second overlapping portions of the sensed electrical signal. For example, a portable AED can include such a circuit to sense first and second overlapping sections of an ECG. By utilizing this overlapping-window technique, the AED can obtain and analyze multiple sections of ECG data, and thus can make a shock / no-shock decision, more quickly than an AED using contiguous-window analysis. Thus, the overlapping-window technique allows one to use both longer ECG sections (better accuracy per window) and more of these longer sections (better voting accuracy) over a given analysis time. Furthermore, this overlapping-window technique significantly reduces or eliminates boundary problems because the boundary of one ECG section is within the interior of either the preceding or the following overlapping ECG section.

Description

TECHNICAL FIELD[0001]The invention relates generally to electronic circuits and systems, and more particularly to a circuit and method for analyzing a patient's heart function using overlapping analysis windows. For example, a portable automatic external defibrillator (AED) can analyze overlapping portions of an electrocardiogram (ECG) to determine if a patient's heart would benefit from a defibrillating shock. By analyzing overlapping portions of the patient's ECG, the AED often makes a shock / no-shock decision more quickly and more accurately than AEDs using other analysis techniques.BACKGROUND OF THE INVENTION[0002]Portable AEDs have saved many lives in non-hospital settings and, as a result of advances in AED technology, the number of lives saved per year is rising. Typically, a portable AED analyzes a patient's heart function and instructs an operator to administer an electrical shock if appropriate. For example, a shock can often revive a patient who is experiencing ventricular...

AI Technical Summary

Benefits of technology

[0015]For example, a portable AED can include such a circuit to sense a first section of an ECG during a first time period and to sense a second section of the ECG during a second time period that overlaps the first time period. By utilizing this overlapping-window technique, the AED can obtain and analyze multiple sections of ECG data, and thus can make a shock / no-shock decision, more quickly than an AED using contiguous-window analysis. Thus, the overlapping-window technique allows one to use both longer ECG sections (better accuracy per window) and more of these longer sections (better voting accuracy) over a given analysis time. Furthermore, this overlapping-window technique significantly reduces or eliminates boundary problems because the boundary of one ECG section is within the interior of one or more of the either the preceding or the following overlapping ECG sections.

Problems solved by technology

Because older models of portable AEDs include only basic diagnostic and safety features, they are often difficult to operate.

Therefore, only specially trained persons such as emergency medical technicians (EMTs) can use these older models to administer shocks.

Unfortunately, many people do not know how to administer CPR.

Therefore, even if the patient is discovered immediately, the AED often has less than a minute to diagnose and shock the patient before he / she is in danger of suffering permanent brain damage.

Unfortunately, many portable AEDs implement heart-analysis techniques that require a relatively long time to analyze the patient's ECG and to make a shock / no-shock decision based on the analysis.

Referring to FIG. 1, an AED (not shown in FIG. 1) using contiguous windowing often requires a relatively long time to make a shock / no-shock decision.

In addition, changes in the patient's heart function may increase the time that the AED requires to make a shock / no-shock decision.

Furthermore, although in this example the transition from normal sinus rhythm to VF occurs near the boundary between the ECG sections 10a and 10b, the same problem often arises when the transition occurs within a section 10.

If all the sections 10 are too small, the AED makes a series of inaccurate analyses that may cause the AED to make an inaccurate shock / no-shock decision.

In addition, referring to FIG. 2, even when the ECG sections are not too short, an AED (not shown in FIG. 2) using contiguous windowing may incorrectly diagnose a patient's heart condition, and thus may determine that a defibrillating shock will benefit a patient when in actuality the shock may harm the patient.

Unfortunately, shocking a patient experiencing bradycardia is at best useless and at worst can send the patient into VF or cause other cardiac damage.

These sections may be incorrectly interpreted as benefiting from a shock, resulting in an inappropriate shock diagnosis.

Still referring to FIG. 2, there are currently no analysis techniques for overcoming the intersecting-boundary problem other than to vote among multiple contiguous ECG sections, thereby delaying diagnosis, or to have a skilled operator (not shown in FIG. 2) study the ECG and determine if the AED's shock / no-shock decision is correct.

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